Stacked thin film transistors with nanowires

ABSTRACT

Thin film transistor structures and processes are disclosed that include stacked nanowire bodies to mitigate undesirable short channel effects, which can occur as gate lengths scale down to sub-100 nanometer (nm) dimensions, and to reduce external contact resistance. In an example embodiment, the disclosed structures employ a gate-all-around architecture, in which the gate stack (including a high-k dielectric layer) wraps around each of the stacked channel region nanowires (or nanoribbons) to provide improved electrostatic control. The resulting increased gate surface contact area also provides improved conduction. Additionally, these thin film structures can be stacked with relatively small spacing (e.g., 1 to 20 nm) between nanowire bodies to increase integrated circuit transistor density. In some embodiments, the nanowire body may have a thickness in the range of 1 to 20 nm and a length in the range of 5 to 100 nm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a U.S. National Phase Application under 35U.S.C. § 371 of International Application No. PCT/US2018/013570, filedon Jan. 12, 2018, the entire contents of which is hereby incorporated byreference herein.

BACKGROUND

A thin film transistor (TFT) is generally fabricated by depositing thinfilms of an active semiconductor layer as well as a dielectric layer andmetallic contacts over a substrate. There are a number of non-trivialperformance issues associated with TFTs.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of embodiments of the claimed subject matterwill become apparent as the following Detailed Description proceeds, andupon reference to the Drawings, wherein like numerals depict like parts.

FIGS. 1A and 1B illustrate a method of forming an integrated circuit(IC) including stacked nanowire thin film transistors, in accordancewith some embodiments of the present disclosure.

FIGS. 2-13 illustrate example IC structures that are formed whencarrying out the method of FIGS. 1A and 1B, in accordance with someembodiments

FIG. 14 illustrates an example cross-sectional view along the plane C-Cin FIG. 2, in accordance with some embodiments.

FIG. 15 illustrates a computing system implemented with integratedcircuit structures and/or transistor devices formed using the techniquesdisclosed herein, in accordance with some embodiments of the presentdisclosure.

These and other features of the present embodiments will be understoodbetter by reading the following detailed description, taken togetherwith the figures herein described. In the drawings, each identical ornearly identical component that is illustrated in various figures may berepresented by a like numeral. For purposes of clarity, not everycomponent may be labeled in every drawing. Furthermore, as will beappreciated, the figures are not necessarily drawn to scale or intendedto limit the described embodiments to the specific configurations shown.For instance, while some figures generally indicate straight lines,right angles, and smooth surfaces, an actual implementation of thedisclosed techniques may have less than perfect straight lines and rightangles, and some features may have surface topography or otherwise benon-smooth, given real-world limitations of fabrication processes.Further still, some of the features in the drawings may include apatterned and/or shaded fill, which is merely provided to assist invisually differentiating the different features. In short, the figuresare provided merely to show example structures

Although the following Detailed Description will proceed with referencebeing made to illustrative embodiments, many alternatives,modifications, and variations thereof will be apparent in light of thisdisclosure.

DETAILED DESCRIPTION

Thin film transistor (TFT) structures, and processes for fabrication ofthose structures, are disclosed which include stacked nanowire bodies tomitigate undesirable short channel effects (SCE) and reduce externalcontact resistance (Rext). In an example embodiment, the disclosedstructures employ a gate-all-around (GAA) architecture, in which thegate structure includes a high-k dielectric layer and a metal gate layerwrapped around each of the stacked nanowire bodies to provide improvedelectrostatic control. The resulting increased gate surface contact areaalso provides improved electrical conduction, as will be explained ingreater detail below. Additionally, these thin film structures can bestacked with relatively small spacing between nanowire bodies (e.g., inthe range of 1 to 20 nm) to increase transistor density on theintegrated circuit. In some embodiments, the nanowire bodies may have athickness in the range of 1 to 20 nm, and a length (e.g., between sourceand drain regions) in the range of 5 to 100 nm. In some embodiments, upto 10 or more nanowire bodies may be stacked to increase currenthandling capability of the TFT. Numerous configurations and processflows will be apparent in light of this disclosure.

General Overview

As transistor devices are scaled down to include smaller criticaldimensions, and in particular, as gate lengths decrease below 100 nm(and especially below 50 nm), SCE problems can arise. These problemstypically include, for example, increased current leakage from source todrain regions, reduced contact resistance which limits transistorcurrent handling capacity, and degraded subthreshold swingcharacteristics (e.g., the ratio of gate-source voltage to drain-sourcecurrent) which reduces switching speed.

Thus, and in accordance with numerous embodiments of the presentdisclosure, techniques are provided for forming TFT structures thatinclude stacked nanowire bodies comprising the source, gate (orchannel), and drain regions of the transistor. As can be understoodbased on this disclosure, a gate dielectric layer and a metal gate layeror so-called electrode wrap around each of the stacked nanowires (ornanoribbons) to provide improved electrostatic control and increasedcontact surface area for the gate, with the gate dielectric layer beingbetween the metal gate layer and the corresponding nanowire body. Insome embodiments, the nanowire body includes an oxide semiconductormaterial, such as indium gallium zinc oxide (IGZO), zinc oxide, indiumoxide, aluminum zinc oxide, gallium oxide, indium zinc oxide, indium tinoxide, copper oxide, and/or zinc tin oxide. In some embodiments, thenanowire body may include group III-V semiconductor materials, such asindium gallium arsenide, and/or indium phosphide. In some embodiments,the nanowire body may include silicon, germanium, and/or silicongermanium. The gate dielectric may include a high-k gate dielectricmaterial, in some embodiments.

Note that, as used herein, the expression “X includes at least one of Aand B” refers to an X that may include, for example, just A only, just Bonly, or both A and B. To this end, an X that includes at least one of Aand B is not to be understood as an X that requires each of A and B,unless expressly so stated. For instance, the expression “X includes Aand B” refers to an X that expressly includes both A and B. Moreover,this is true for any number of items greater than two, where “at leastone of” those items is included in X. For example, as used herein, theexpression “X includes at least one of A, B, and C” refers to an X thatmay include just A only, just B only, just C only, only A and B (and notC), only A and C (and not B), only B and C (and not A), or each of A, B,and C. This is true even if any of A, B, or C happens to includemultiple types or variations. To this end, an X that includes at leastone of A, B, and C is not to be understood as an X that requires each ofA, B, and C, unless expressly so stated. For instance, the expression “Xincludes A, B, and C” refers to an X that expressly includes each of A,B, and C. Likewise, the expression “X included in at least one of A andB refers to an X that may be included, for example, in just A only, injust B only, or in both A and B. The above discussion with respect to “Xincludes at least one of A and B” equally applies here, as will beappreciated.

Use of the techniques and structures provided herein may be detectableusing tools such as: photo-luminescence detection, electron microscopyincluding scanning/transmission electron microscopy (SEM/TEM), scanningtransmission electron microscopy (STEM), nano-beam electron diffraction(NBD or NBED), and reflection electron microscopy (REM); compositionmapping; x-ray crystallography or diffraction (XRD); energy-dispersivex-ray spectroscopy (EDS); secondary ion mass spectrometry (SIMS);time-of-flight SIMS (ToF-SIMS); atom probe imaging or tomography; localelectrode atom probe (LEAP) techniques; 3D tomography; or highresolution physical or chemical analysis, to name a few suitable exampleanalytical tools. In particular, in some embodiments, such tools mayindicate an integrated circuit including stacked nanowire thin filmtransistors, as described herein.

In some embodiments, the techniques and structures described herein maybe detected based on the benefits derived therefrom, such as byobserving a thin film transistor structure with sub-100 nm gate lengththat does not exhibit undesirable short channel effects and highexternal contact resistance. Numerous configurations and variations willbe apparent in light of this disclosure.

Methodology and Architecture

FIG. 1 (1A and 1B) illustrate method 100 of forming an integratedcircuit (IC) including stacked nanowire thin film transistors, inaccordance with some embodiments of the present disclosure. FIGS. 2through 13 illustrate example IC structures that are formed whencarrying out method 100 of FIG. 1, in accordance with some embodiments.The structures of FIGS. 2-13 are depicted and described herein ascomprising a stack of two TFT layers, for ease of illustration. However,in some embodiments, the disclosed techniques can be used to form a TFTstack of any desired number of layers, for example up to 10 layers ormore, as can be understood based on this disclosure. Numerous variationsand configurations will be apparent in light of this disclosure.

Turning initially to FIG. 2, a perspective view of a stacked TFTstructure is shown at a high level, in which many details are omittedfor illustration clarity. These details will be shown and described inthe later figures. The TFT structure in this example includes 2 thinfilm layers 202 above the substrate 204. The TFT is shown to besegmented into three regions, along the Z-axis. These regions include asource (or drain) region 400, a gate region 300, and a drain (or source)region 400. Cross-section A-A, through the gate region 300 in the X-Yplane, is illustrated in greater detail in FIG. 3. Cross-section B-B,through the S/D region 400 in the X-Y plane, is illustrated in greaterdetail in FIG. 4. Cross-section C-C, in the Y-Z plane, is illustrated ingreater detail in FIG. 14.

FIG. 3 illustrates an example cross-sectional view A-A of the gateregion 300. Gate thin film material 202 a (i.e., the section of thinfilm 202 in the gate region) is shown to be wrapped with a gatedielectric layer 308 on all 4 sides. In some embodiments, thecross-sectional dimensions of the gate thin film 202 a may be in therange of 1-100 nm and more specifically in the range of 1-20 nm. In someembodiments, the gate thin film material may include indium gallium zincoxide (InGaZnO, also referred to as IGZO), although other materials arepossible such as, for example, zinc oxide, indium oxide, aluminum zincoxide, gallium oxide, indium zinc oxide, indium tin oxide, copper oxide,zinc tin oxide, indium gallium arsenide, indium phosphide, silicon,germanium, and/or silicon germanium.

In some embodiments, the gate dielectric layer 308 includes a dielectricmaterial such as silicon dioxide and/or a high-k dielectric materialsuch as hafnium dioxide, hafnium silicon oxide, hafnium zirconium oxide,zirconium oxide, hafnium silicon oxide, lanthanum oxide, lanthanumaluminum oxide, zirconium silicon oxide, tantalum oxide, titanium oxide,barium strontium titanium oxide, barium titanium oxide, strontiumtitanium oxide, yttrium oxide, aluminum oxide, lead scandium tantalumoxide, and/or lead zinc niobate. In some embodiments, an annealingprocess may be carried out on the gate dielectric layer 308 to improveits quality when a high-k material is used. In any such embodiments, thespacing between gate thin film layers (along the Y-axis) may be in therange of 1-100 nm and more specifically in the range of 1-20 nm. Thedielectric layer 308 eliminates the need for additional passivationlayers between each of the stacked gate thin film layers.

Metal gate structure 304 is shown to encompass the wrapped thin filmlayers 202 a in the gate or so-called channel area, and may serve as anelectrical contact for the gate. In some embodiments, the metal gatestructure, also referred to herein as a gate electrode structure, mayinclude a wide range of suitable metals or metal alloys, such astitanium nitride (TiN) or tungsten or aluminum or titanium, or tantalum,or copper, or tantalum nitride, or a combination thereof (e.g., tungstencore with TiN on sides of core for work function). Numerous gateelectrode materials and structures can be used. Tip spacers 306 areshown adjacent to the metal gate 304 and serve to help insulate the gatefrom the source and drain. In some embodiments, the tip spacers mayinclude any suitable electrical insulator, dielectric, oxide (e.g.,silicon oxide), and/or nitride (e.g., silicon nitride) material.Isolation material 302 is shown adjacent to the tip spacers 306 andserves to isolate this TFT from any adjacent TFTs. In some embodiments,isolation material 302 may also include any suitable electricallyinsulating material, such as one or more dielectric, oxide (e.g.,silicon dioxide), and/or nitride (e.g., silicon nitride) materials. Thegate region is disposed on an underlying substrate layer 204 which, insome embodiments, may include an insulating oxide layer, although othermaterials are possible as will be explained below.

In some embodiments, the structures for gate dielectric 308 and/or gateelectrode 304 may include any number of discrete layers and in somecases are multilayer structures of two or more material layers. Forinstance, in one such embodiment, the gate dielectric 308 is a bi-layerstructure having a first dielectric material (e.g., silicon dioxide) incontact with the channel region (gate thin film 202 a) and a seconddielectric material (e.g., hafnium oxide) in contact with the firstdielectric material, the first dielectric material having a dielectricconstant that is lower than the dielectric constant of the seconddielectric material. Likewise, the gate electrode 304 structure mayinclude a central metal plug portion (e.g., tungsten) with one or moreouter work function layers and/or barrier layers (e.g., tantalum,tantalum nitride), and/or a resistance reducing cap layer (e.g., copper,gold). In some embodiments, the gate dielectric and/or gate electrodemay include grading (increasing or decreasing, as the case may be) ofthe concentration of one or more materials therein. In a more generalsense, any number of suitable gate structure configurations can be used,as will be appreciated.

FIG. 4 illustrates an example cross-sectional view B-B of the S/D region400. S/D thin film material 202 b (i.e., the section of thin film 202extending into the S/D region) may also include IGZO in someembodiments, although other materials are possible as will be explainedbelow. The S/D thin film material 202 b may also, however, be doped toachieve desired S/D characteristics for the TFT device. In someembodiments, the doping process may include forming oxygen vacancies inthe IGZO and/or introducing impurities (e.g., n-type and/or p-typeimpurities).

An S/D metal structure 404 is shown to encompass the S/D thin filmlayers 202 b, and may serve as an electrical contact for the source anddrain. In some embodiments, the S/D metal structure may include titaniumnitride (TiN), although other materials are possible such as, forexample, titanium, tantalum nitride, cobalt, tungsten, copper nickel,tantalum, gold, gold-germanium, nickel-platinum, and/or nickel aluminum.Isolation material 302 is shown adjacent to the S/D metal 404 and servesto isolate this TFT from any adjacent TFTs. In some embodiments,isolation material 302 may include any suitable electrically insulatingmaterial, such as one or more dielectric, oxide (e.g., silicon dioxide),and/or nitride (e.g., silicon nitride) materials. The S/D region isdisposed on the underlying substrate layer 204. In some embodiments, thegate thin film material 202 a of the nanowire body may be thinner (e.g.,along the Y-axis) than at least one of the S/D thin film layers 202 b.

Referring now to FIG. 1A, method 100, for forming an integrated circuitaccording to an embodiment of the present disclosure, commences atoperation 102 with depositing alternating layers of sacrificial materialand gate thin film material (e.g., nanowires or nanoribbons) on asubstrate in the gate region 300. For example (with reference to FIG.5A, which illustrates the resulting structure in the gate region 300, inaccordance with some embodiments) a first layer of sacrificial material504 is deposited on substrate 204 followed by deposition of a first gatethin film layer 202 a on top of the sacrificial material. The process isrepeated with the deposition of a second sacrificial material layer anda second gate thin film layer. In some embodiments, deposition may beperformed using any suitable technique, in light of the presentdisclosure. For example, deposition may be performed using chemicalvapor deposition (CVD), atomic layer deposition (ALD), physical vapordeposition (PVD), molecular beam epitaxy (MBE), or spin-on processing.In some embodiments, the spacing (e.g., along the Y-axis) between thefirst and second gate thin film layers is in the range of 1 to 20 nm,and the thickness of the gate thin film layers (e.g., along the Y-axis)is also in the range of 1-20 nm.

In some embodiments, the gate thin film layers 202 a may include atleast one metal oxide, such as indium gallium zinc oxide (InGaZnO, alsoreferred to as IGZO), gallium oxide, indium oxide, indium zinc oxide,indium tin oxide, copper oxide, zinc oxide, aluminum doped zinc oxide,and/or zinc tin oxide, to name a few examples. In some such embodiments,the metal oxide material (which in some cases may also be considered asemiconducting material, and more specifically, an oxide semiconductormaterial) may have a single crystal or monocrystalline (or simply,crystalline) structure (e.g., crystalline IGZO), an amorphouscrystalline structure (e.g., amorphous IGZO), or a crystalline structurein between that may be referred to as a polycrystalline structure (e.g.,polycrystalline IGZO). Further, in some such embodiments, the metaloxide material may have other type of crystalline structures, such as aC-axis aligned crystalline (CAAC) structure (e.g., CAAC IGZO) or ananocrystalline structure (e.g., nanocrystalline IGZO). Note that theseother types of crystalline structures may be well suited for productionpurposes because of their relatively low thermal budget requirements(that can be suitable with back-end-of-line processing, such as thermalbudgets of 400-600 degrees Celsius), relatively low cost, relativelyhigh throughput, and relatively high reliability.

In some embodiments, the gate thin film layers 202 a may includeamorphous, polycrystalline, or monocrystalline group IV and/or groupIII-V semiconductor material, such as silicon, germanium, silicongermanium, gallium arsenide, or indium gallium arsenide, to name a fewexamples. In some such embodiments, the group IV and/or group III-Vsemiconductor material, where employed may be grown at low temperatures,particularly at back-end-of-line (BEOL) IC locations. Note that the useof “group IV semiconductor material” (or “group IV material” orgenerally, “IV”) herein includes at least one group IV element (e.g.,silicon, germanium, carbon, tin), such as silicon (Si), germanium (Ge),silicon germanium (SiGe), and so forth. The use of “group III-Vsemiconductor material” (or “group III-V material” or generally,“III-V”) herein includes at least one group III element (e.g., aluminum,gallium, indium) and at least one group V element (e.g., nitrogen,phosphorus, arsenic, antimony, bismuth), such as gallium arsenide(GaAs), indium gallium arsenide (InGaAs), indium aluminum arsenide(InAlAs), gallium phosphide (GaP), gallium antimonide (GaSb), indiumphosphide (InP), and so forth. Note that group III may also be known asthe boron group or IUPAC group 13, group IV may also be known as thecarbon group or IUPAC group 14, and group V may also be known as thenitrogen family or IUPAC group 15, for example.

Substrate 204, in some embodiments, may be: a bulk substrate includinggroup IV semiconductor material (e.g., Si, Ge, SiGe), group III-Vsemiconductor material (e.g., GaAs, GaAsSb, GaAsIn), and/or any othersuitable material(s) as will be apparent in light of this disclosure; anX on insulator (XOI) structure where X is one of the aforementionedmaterials (e.g., group IV and/or group III-V semiconductor material) andthe insulator material is an oxide material or dielectric material orsome other electrically insulating material, such that the XOI structureincludes the electrically insulating material layer between twosemiconductor layers; or some other suitable multilayer structure wherethe top layer includes one of the aforementioned semiconductor materials(e.g., group IV and/or group III-V semiconductor material). The use of“group IV semiconductor material” (or “group IV material” or generally,“IV”) herein includes at least one group IV element (e.g., silicon,germanium, carbon, tin), such as silicon (Si), germanium (Ge), silicongermanium (SiGe), and so forth. The use of “group III-V semiconductormaterial” (or “group III-V material” or generally, “III-V”) hereinincludes at least one group III element (e.g., aluminum, gallium,indium) and at least one group V element (e.g., nitrogen, phosphorus,arsenic, antimony, bismuth), such as gallium arsenide (GaAs), indiumgallium arsenide (InGaAs), indium aluminum arsenide (InAlAs), galliumphosphide (GaP), gallium antimonide (GaSb), indium phosphide (InP), andso forth. Note that group III may also be known as the boron group orIUPAC group 13, group IV may also be known as the carbon group or IUPACgroup 14, and group V may also be known as the nitrogen family or IUPACgroup 15, for example.

Although substrate 204, in this example embodiment, is shown as having athickness (dimension in the Y-axis direction) similar to other layersshown in subsequent structures for ease of illustration, in someinstances, substrate 204 may be much thicker than the other layers, suchas having a thickness in the range of 50 to 950 microns, for example, orany other suitable thickness as will be apparent in light of thisdisclosure. In some embodiments, substrate 204 may be used for one ormore other IC devices, such as various diodes (e.g., light-emittingdiodes (LEDs) or laser diodes), various transistors (e.g., MOSFETs orTFETs), various capacitors (e.g., MOSCAPs), variousmicroelectromechanical systems (MEMS), various nanoelectromechanicalsystems (NEMS), various radio frequency (RF) devices, various sensors,or any other suitable semiconductor or IC devices, depending on the enduse or target application. Accordingly, in some embodiments, thestructures described herein may be included in a system-on-chip (SoC)application, as will be apparent in light of this disclosure.

Further note that, while the structures shown in this and other figures,as being relatively rectangular in nature (with straight sides and aflat top) for ease of depiction, in reality, they may include a taperedor otherwise varying profile where some portions of the structure arenarrower than other portions. Moreover, some portions may be rounded,rather than flat. Numerous other real-world geometries will beappreciated.

Method 100 of FIG. 1 continues with performing, at operation 104, thedepositing of alternating layers of sacrificial material and S/D thinfilm material (e.g., nanowires or nanoribbons) on a substrate in the S/Dregion 400. For example (with reference to FIG. 5B, which illustratesthe resulting structure in the S/D region 400, in accordance with someembodiments) a first layer of sacrificial material 504 is deposited onsubstrate 204 followed by deposition of a first S/D thin film layer 202b on top of the sacrificial material. The process is repeated with thedeposition of a second sacrificial material layer and a second S/D thinfilm layer. In some embodiments, the spacing (e.g., along the Y-axis)between the first and second S/D thin film layers is in the range of 1to 20 nm, and the thickness of the S/D thin film layers (e.g., along theY-axis) is also in the range of 1-20 nm.

In some embodiments, the S/D thin film material 202 b may be the same orsimilar in composition to the gate thin film material 202 a, withadditional processing, however, to include doping to form oxygenvacancies and/or to introduce impurities (e.g., n-type and/or p-typeimpurities) to achieve desired resulting S/D region characteristics forthe TFT device being formed. In some such embodiments, oxygen vacanciesmay be formed on the surface of the S/D thin film layer 202 b, such asvia plasma treatment to damage the surfaces, chemical treatment toextract material from the layer (e.g., extract indium, gallium, and/orzinc from IGZO) to form a modified surface that has higher oxygenvacancies, an -idation type of treatment (e.g., silicidation orIII-V-idation type of reaction) to strip the S/D surfaces of oxygen andleave vacancies, and/or any other suitable processing as can beunderstood based on this disclosure.

In some embodiments, the S/D thin film material 202 b may include indiumtin oxide. In some embodiments, the S/D thin film material 202 b mayinclude titanium, titanium nitride, or tantalum nitride, each incombination with a more conductive material such as cobalt, tungsten, orcopper. In some embodiments, the S/D thin film material 202 b mayinclude indium arsenic applied through epitaxial deposition.

Method 100 of FIG. 1 continues with the formation, at operation 106, ofdummy gate material 602, tip spacer 306, and isolation material 302 overthe gate region 300, resulting in the structure illustrated in FIG. 6A,in accordance with some embodiments. Operation 106 may compriseindividual sub operations such as, for example: depositing the dummygate material 602; etching that material back and depositing materialfor the tip spacer 306 adjacent to the dummy gate, and then depositingthe isolation material 302 adjacent to the tip spacer.

In some embodiments, tip spacers 306 may include any suitable material,such as any suitable electrical insulator, dielectric, oxide (e.g.,silicon oxide), and/or nitride (e.g., silicon nitride) material, as willbe apparent in light of this disclosure.

In some embodiments, isolation material 302 may include any suitableelectrically insulating material, such as one or more dielectric, oxide(e.g., silicon dioxide), and/or nitride (e.g., silicon nitride)materials. In some embodiments, the isolation material 302 may beselected based on the material of substrate 204. For instance, in thecase of a Si substrate, the isolation material may be selected to besilicon dioxide or silicon nitride, to provide some examples.

Etching may be performed using any suitable process including wet/dryetching, selective/non-selective etching, and/or lithography. Etchingmay further include masking operations to help prevent the etching fromconsuming material in an undesired manner or from removing selectedregions that are to be protected.

Method 100 of FIG. 1 continues with the deposition, at operation 108, ofisolation material 302 over the S/D region 400, resulting in thestructure illustrated in FIG. 6B, in accordance with some embodiments.

Method 100 of FIG. 1 continues, at operation 110, with removal of thedummy gate material 602 from the gate region 300, resulting in thestructure illustrated in FIG. 7, and removal of the sacrificial material504 from the gate region 300, resulting in the structure illustrated inFIG. 8, in accordance with some embodiments. At this stage in theprocess flow, after removal of the sacrificial material, the gate thinfilm structures 202 a are supported by the extension of the thin filminto the S/D regions (S/D thin film 202 b) and the isolation material302 of the S/D region. The removal of dummy gate material 602 andsacrificial material 504 may be accomplished, for example, through anetching process.

Method 100 of FIG. 1 continues, at operation 112, with the deposition ofa high-k dielectric material 308 around the gate thin film 202 a,resulting in the structure illustrated in FIG. 9, in accordance withsome embodiments. Examples of high-k dielectric materials include, forinstance, hafnium oxide, hafnium silicon oxide, lanthanum oxide,lanthanum aluminum oxide, zirconium oxide, zirconium silicon oxide,tantalum oxide, titanium oxide, barium strontium titanium oxide, bariumtitanium oxide, strontium titanium oxide, yttrium oxide, aluminum oxide,lead scandium tantalum oxide, and lead zinc niobate.

Method 100 of FIG. 1 (referring now to FIG. 1B) continues, at operation114, with the deposition of metal gate material 304 around the high-kmaterial 308, resulting in the structure illustrated in FIG. 10, inaccordance with some embodiments. The metal gate material 304 serves asan electrical contact to the gate. In some embodiments, the metal gatematerial 304 may include titanium nitride or other suitable electricallyconductive material. At this stage, a planarization and/or polishingoperation may be performed over the top of the gate region using anysuitable techniques such as chemical-mechanical planarization/polishing(CMP) processes, for example.

Method 100 of FIG. 1 continues, at operation 116, with etching out of aportion of the isolation material 302 from the S/D region 400. Theportion to be etched is adjacent to, and on top of, the S/D thin filmlayers 202 b. The removal of this portion results in the structureillustrated in FIG. 11, in accordance with some embodiments.

Method 100 of FIG. 1 continues, at operation 118, with etching out ofthe sacrificial material 504 from the S/D region, resulting in thestructure illustrated in FIG. 12, in accordance with some embodiments.At this stage in the process flow, after removal of the sacrificialmaterial, the S/D thin film structures 202 b are supported by theextension of the thin film into the gate region (gate thin film 202 a)and the isolation material 302 of the gate region.

Method 100 of FIG. 1 continues, at operation 120, with the deposition ofS/D metal material 404 around the S/D thin film material 202 b in theS/D region 400, resulting in the structure illustrated in FIG. 13, inaccordance with some embodiments. The S/D metal material 404 serves asan electrical contact to the source and drains. In some embodiments, theS/D metal material 404 may include titanium nitride or other suitableelectrically conductive material. At this stage, a planarization and/orpolishing operation may be performed over the top of the S/D regionusing any suitable techniques such as CMP, for example.

Method 100 of FIG. 1 continues, at operation 122, with completingintegrated circuit (IC) processing as desired, in accordance with someembodiments. Such additional processing to complete the IC may includeback-end or back-end-of-line (BEOL) processing to form one or moremetallization layers and/or to interconnect the transistor devicesformed during front-end or front-end-of-line (FEOL) processing, forexample. For example, a metallization layer may be formed between thebottom most thin film transistor of the stack and the substrate. Anyother suitable processing may be performed, as will be apparent in lightof this disclosure. Note that the processes 102-122 of method 100 areshown in a particular order for ease of description. However, one ormore of the processes 102-122 may be performed in a different order ormay not be performed at all. For example, in some embodiments, the S/Dregion 400 may be formed before the gate region 300. Recall that thetechniques may be used to form a multitude of different transistor typesand configurations. Numerous variations and configurations will beapparent in light of the present disclosure.

FIG. 14 illustrates an example cross-sectional view along the plane C-Cin FIG. 2, in accordance with some embodiments. The cross-sectional viewof FIG. 14 is provided to assist in illustrating different features ofthe structure of FIG. 2 in conjunction with the details shown in FIG. 3for the gate region and FIG. 4 for the S/D regions. Therefore, therelevant description with respect to each similarly numbered feature inFIGS. 2-4 is equally applicable to FIG. 14. However, note that thedimensions of the features shown in FIG. 14 may differ relative to thefeatures in FIGS. 2-4, for ease of illustration.

For each of the two TFT layers, the gate thin film structure 202 a isshown to be surrounded on top and bottom (through the cross-section) bythe high-k layer 308, which in turn is surrounded on top and bottom bythe metal gate layer 304. Shown to the left and right of the gate thinfilm structure 202 a are the source and drain thin film structures 202b. Shown above and below the S/D thin film structures 202 b are the S/Dmetal layers 404. Gate spacers 210 are also shown to separate the S/Dmetal layers 404 from the adjacent metal gate layers 304 to preventelectrical shorting. Spacers 210 may include any suitable material, suchas any suitable electrical insulator, dielectric, oxide (e.g., siliconoxide), and/or nitride (e.g., silicon nitride) material, as will beapparent in light of this disclosure.

In some embodiments, the length of the gate thin film structure, ornanowire body, 202 a (e.g., along the Z-axis from the source region tothe drain region) may be in the range of 5 nm to 100 nm. In someembodiments, the thickness of the thin film structures, or nanowirebodies, 202 a and 202 b, may be in the range of 1 nm to 20 nm (e.g.,along the Y-axis). In some embodiments, the spacing between the thinfilm structures, or nanowire bodies, 202 a and 202 b, may be in therange of 1 nm to 20 nm (e.g., along the Y-axis).

In some embodiments, the techniques enable maintaining a desired deviceperformance when scaling to such low thresholds, such as sub-50, sub-40,sub-30, or sub-20 nm thresholds and beyond, as can be understood basedon this disclosure. For instance, the techniques as variously describedherein can reduce short channel effects to provide improved gate controlto enable faster switching speeds, and improved conduction to allow forincreased current handling capacity.

Example System

FIG. 15 illustrates a computing system 1000 implemented with integratedcircuit structures and/or transistor devices formed using the techniquesdisclosed herein, in accordance with some embodiments of the presentdisclosure. As can be seen, the computing system 1000 houses amotherboard 1002. The motherboard 1002 may include a number ofcomponents, including, but not limited to, a processor 1004 and at leastone communication chip 1006, each of which can be physically andelectrically coupled to the motherboard 1002, or otherwise integratedtherein. As will be appreciated, the motherboard 1002 may be, forexample, any printed circuit board, whether a main board, adaughterboard mounted on a main board, or the only board of system 1000,etc.

Depending on its applications, computing system 1000 may include one ormore other components that may or may not be physically and electricallycoupled to the motherboard 1002. These other components may include, butare not limited to, volatile memory (e.g., DRAM), non-volatile memory(e.g., ROM), a graphics processor, a digital signal processor, a cryptoprocessor, a chipset, an antenna, a display, a touchscreen display, atouchscreen controller, a battery, an audio codec, a video codec, apower amplifier, a global positioning system (GPS) device, a compass, anaccelerometer, a gyroscope, a speaker, a camera, and a mass storagedevice (such as hard disk drive, compact disk (CD), digital versatiledisk (DVD), and so forth). Any of the components included in computingsystem 1000 may include one or more integrated circuit structures ordevices formed using the disclosed techniques in accordance with anexample embodiment. In some embodiments, multiple functions can beintegrated into one or more chips (e.g., for instance, note that thecommunication chip 1006 can be part of or otherwise integrated into theprocessor 1004).

The communication chip 1006 enables wireless communications for thetransfer of data to and from the computing system 1000. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 1006 may implementany of a number of wireless standards or protocols, including, but notlimited to, Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE,GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well asany other wireless protocols that are designated as 3G, 4G, 5G, andbeyond. The computing system 1000 may include a plurality ofcommunication chips 1006. For instance, a first communication chip 1006may be dedicated to shorter range wireless communications such as Wi-Fiand Bluetooth and a second communication chip 1006 may be dedicated tolonger range wireless communications such as GPS, EDGE, GPRS, CDMA,WiMAX, LTE, Ev-DO, and others.

The processor 1004 of the computing system 1000 includes an integratedcircuit die packaged within the processor 1004. In some embodiments, theintegrated circuit die of the processor includes onboard circuitry thatis implemented with one or more integrated circuit structures or devicesformed using the disclosed techniques, as variously described herein.The term “processor” may refer to any device or portion of a device thatprocesses, for instance, electronic data from registers and/or memory totransform that electronic data into other electronic data that may bestored in registers and/or memory.

The communication chip 1006 also may include an integrated circuit diepackaged within the communication chip 1006. In accordance with somesuch example embodiments, the integrated circuit die of thecommunication chip includes one or more integrated circuit structures ordevices formed using the disclosed techniques as variously describedherein. As will be appreciated in light of this disclosure, note thatmulti-standard wireless capability may be integrated directly into theprocessor 1004 (e.g., where functionality of any chips 1006 isintegrated into processor 1004, rather than having separatecommunication chips). Further note that processor 1004 may be a chip sethaving such wireless capability. In short, any number of processor 1004and/or communication chips 1006 can be used. Likewise, any one chip orchip set can have multiple functions integrated therein.

In various implementations, the computing system 1000 may be a laptop, anetbook, a notebook, a smartphone, a tablet, a personal digitalassistant (PDA), an ultra-mobile PC, a mobile phone, a desktop computer,a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player, adigital video recorder, or any other electronic device or system thatprocesses data or employs one or more integrated circuit structures ordevices formed using the disclosed techniques, as variously describedherein. Note that reference to a computing system is intended to includecomputing devices, apparatuses, and other structures configured forcomputing or processing information.

Further Example Embodiments

The following examples pertain to further embodiments, from whichnumerous permutations and configurations will be apparent.

Example 1 is an integrated circuit (IC) comprising: a nanowire bodyincluding an oxide semiconductor material including first, second, andthird portions, the second portion between the first and third portions,the first portion being a source region and the third portion being adrain region; a gate dielectric structure disposed around the secondportion of the nanowire body; and a gate electrode structure disposedaround the gate dielectric structure, the gate electrode structurecomprising metal.

Example 2 includes the subject matter of Example 1, further comprisingone or more additional nanowire bodies stacked within the gate electrodestructure and the gate dielectric structure disposed around theadditional nanowire bodies.

Example 3 includes the subject matter of Examples 1 or 2, wherein thenanowire body and the one or more additional nanowire bodies are spacedapart from each other by a distance in the range of 1 nanometer to 20nanometers.

Example 4 includes the subject matter of any of Examples 1-3, whereinthe number of additional nanowire bodies is in the range of 1 to 10.

Example 5 includes the subject matter of any of Examples 1-4, whereinthe gate dielectric structure comprises a high-k dielectric materialincluding hafnium dioxide (HfO2).

Example 6 includes the subject matter of any of Examples 1-5, whereinthe gate dielectric structure comprises a high-k dielectric materialincluding at least one of hafnium zirconium oxide, zirconium oxide,hafnium silicon oxide, lanthanum oxide, lanthanum aluminum oxide,zirconium silicon oxide, tantalum oxide, titanium oxide, bariumstrontium titanium oxide, barium titanium oxide, strontium titaniumoxide, yttrium oxide, aluminum oxide, lead scandium tantalum oxide, andlead zinc niobate.

Example 7 includes the subject matter of any of Examples 1-6, whereinthe oxide semiconductor material includes indium, gallium, zinc, andoxygen.

Example 8 includes the subject matter of any of Examples 1-7, whereinthe oxide semiconductor material includes at least one of zinc oxide,indium oxide, aluminum zinc oxide, gallium oxide, indium zinc oxide,indium tin oxide, copper oxide, zinc tin oxide, indium gallium arsenide,indium phosphide, silicon, germanium, and silicon germanium.

Example 9 includes the subject matter of any of Examples 1-8, whereinthe gate electrode structure includes titanium and nitrogen.

Example 10 includes the subject matter of any of Examples 1-9, whereinthe gate dielectric structure comprises a high-k dielectric material,and the gate electrode structure includes at least one of titaniumnitride, cobalt, tungsten, copper nickel, tantalum, gold,gold-germanium, nickel-platinum, and nickel aluminum.

Example 11 includes the subject matter of any of Examples 1-10, whereinthe second portion of the nanowire body is thinner than at least one ofthe source region and the drain region.

Example 12 includes the subject matter of any of Examples 1-11, whereinat least one of the first and third portions of the nanowire bodyincludes a higher concentration of oxygen vacancies in the oxidesemiconductor material.

Example 13 includes the subject matter of any of Examples 1-12, furthercomprising at least one of a first contact structure disposed around thefirst portion of the nanowire body and a second contact structuredisposed around the third portion of the nanowire body, the first andsecond contact structures comprising metal.

Example 14 includes the subject matter of any of Examples 1-13, furthercomprising at least one of a first gate spacer between the gateelectrode structure and the first metal structure and a second gatespacer between the gate electrode structure and the second metalstructure.

Example 15 includes the subject matter of any of Examples 1-14, whereinthe thickness of the nanowire body is in the range of 1 nanometer to 20nanometers.

Example 16 includes the subject matter of any of Examples 1-15, whereinthe length of the nanowire body from the source region to the drainregion is in the range of 5 nanometers to 100 nanometers, as measuredfrom respective outermost portions of the source and drain regions.

Example 17 includes the subject matter of any of Examples 1-16, furthercomprising an underlying semiconductor substrate.

Example 18 includes the subject matter of any of Examples 1-17, whereinthe underlying semiconductor substrate includes an insulating oxidelayer.

Example 19 includes the subject matter of any of Examples 1-18, furthercomprising at least one interconnect layer between the nanowire body andthe underlying semiconductor substrate, the interconnect layer includingone or more metal features in an insulator material.

Example 20 is a computing system comprising the IC of any of Examples1-19.

Example 21 is a method of forming an integrated circuit (IC), the methodcomprising: forming a nanowire body including an oxide semiconductormaterial, the nanowire body have first, second, and third portions, thesecond portion being between the first and third portions; forming agate dielectric structure disposed around the second portion of thenanowire body; forming a gate electrode structure disposed around thegate dielectric structure; forming a source region in the first portionof the nanowire body and a drain region in the third portion of thenanowire body.

Example 22 includes the subject matter of Example 21, further comprisingforming one or more additional nanowire bodies and forming the gatedielectric structure disposed around the one or more additional nanowirebodies.

Example 23 includes the subject matter of Examples 21 or 22, wherein thenanowire body and the one or more additional nanowire bodies are spacedapart from each other by a distance in the range of 1 nanometer to 20nanometers, and the number of additional nanowire bodies is in the rangeof 1 to 10.

Example 24 includes the subject matter of any of Examples 21-23, whereinthe gate dielectric structure comprises a high-k dielectric materialincluding hafnium dioxide (HfO2).

Example 25 includes the subject matter of any of Examples 21-24, whereinthe gate dielectric structure comprises a high-k dielectric materialincluding at least one of hafnium zirconium oxide, zirconium oxide,hafnium silicon oxide, lanthanum oxide, lanthanum aluminum oxide,zirconium silicon oxide, tantalum oxide, titanium oxide, bariumstrontium titanium oxide, barium titanium oxide, strontium titaniumoxide, yttrium oxide, aluminum oxide, lead scandium tantalum oxide, andlead zinc niobate.

Example 26 includes the subject matter of any of Examples 21-25, whereinthe oxide semiconductor material includes indium, gallium, zinc, andoxygen.

Example 27 includes the subject matter of any of Examples 21-26, whereinthe oxide semiconductor material includes at least one of zinc oxide,indium oxide, aluminum zinc oxide, gallium oxide, indium zinc oxide,indium tin oxide, copper oxide, zinc tin oxide, indium gallium arsenide,indium phosphide, silicon, germanium, and silicon germanium.

Example 28 includes the subject matter of any of Examples 21-27, whereinthe second portion of the nanowire body is thinner than at least one ofthe source region and the drain region.

Example 29 includes the subject matter of any of Examples 21-28, whereinthe thickness of the nanowire body is in the range of 1 nanometer to 20nanometers.

Example 30 includes the subject matter of any of Examples 21-29, whereinthe gate electrode structure includes titanium and nitrogen.

Example 31 includes the subject matter of any of Examples 21-30, whereinthe gate dielectric structure comprises a high-k dielectric material,and the gate electrode structure includes at least one of titaniumnitride, cobalt, tungsten, copper nickel, tantalum, gold,gold-germanium, nickel-platinum, and nickel aluminum.

Example 32 includes the subject matter of any of Examples 21-31, whereinat least one of the first and third portions of the nanowire bodyincludes a higher concentration of oxygen vacancies in the oxidesemiconductor material.

Example 33 includes the subject matter of any of Examples 21-32, furthercomprising forming at least one of a first contact structure disposedaround the first portion of the nanowire body and a second contactstructure disposed around the third portion of the nanowire body, thefirst and second contact structures comprising metal.

Example 34 includes the subject matter of any of Examples 21-33, furthercomprising forming at least one of a first gate spacer between the gateelectrode structure and the first metal structure and a second gatespacer between the gate electrode structure and the second metalstructure.

Example 35 includes the subject matter of any of Examples 21-34, whereinthe length of the nanowire body from the source region to the drainregion is in the range of 5 nanometers to 100 nanometers, as measuredfrom respective outermost portions of the source and drain regions.

Example 36 includes the subject matter of any of Examples 21-35, furthercomprising forming an underlying semiconductor substrate.

Example 37 includes the subject matter of any of Examples 21-36, whereinthe underlying semiconductor substrate includes an insulating oxidelayer.

Example 38 includes the subject matter of any of Examples 21-37, furthercomprising forming at least one interconnect layer between the nanowirebody and the underlying semiconductor substrate, the interconnect layerincluding one or more metal features in an insulator material.

The terms and expressions which have been employed herein are used asterms of description and not of limitation, and there is no intention,in the use of such terms and expressions, of excluding any equivalentsof the features shown and described (or portions thereof), and it isrecognized that various modifications are possible within the scope ofthe claims. Accordingly, the claims are intended to cover all suchequivalents. Various features, aspects, and embodiments have beendescribed herein. The features, aspects, and embodiments are susceptibleto combination with one another as well as to variation andmodification, as will be appreciated in light of this disclosure. Thepresent disclosure should, therefore, be considered to encompass suchcombinations, variations, and modifications. It is intended that thescope of the present disclosure be limited not be this detaileddescription, but rather by the claims appended hereto. Future filedapplications claiming priority to this application may claim thedisclosed subject matter in a different manner, and may generallyinclude any set of one or more elements as variously disclosed orotherwise demonstrated herein.

What is claimed is:
 1. An integrated circuit (IC) comprising: a bodyincluding an oxide semiconductor material including first, second, andthird portions, the second portion between the first and third portions,the first portion being a source region and the third portion being adrain region, and the second portion having a cross-section with amaximum lateral width greater than a maximum vertical height; a gatedielectric structure wrapped around the second portion of the body; anda gate electrode structure wrapped around the gate dielectric structure,the gate electrode structure comprising metal.
 2. The IC of claim 1,further comprising one or more additional bodies, the gate dielectricstructure wrapped around the additional bodies.
 3. The IC of claim 2,wherein the body and the one or more additional bodies are spaced apartfrom each other by a distance in the range of 1 nanometer to 20nanometers.
 4. The IC of claim 2, wherein the number of additionalbodies is in the range of 1 to
 10. 5. The IC of claim 1, wherein thegate dielectric structure comprises a high-k dielectric materialincluding hafnium.
 6. The IC of claim 1, wherein the oxide semiconductormaterial includes indium, gallium, zinc, and oxygen.
 7. The IC of claim1, wherein the oxide semiconductor material includes at least one ofzinc oxide, indium oxide, aluminum zinc oxide, gallium oxide, indiumzinc oxide, indium tin oxide, copper oxide, and zinc tin oxide.
 8. TheIC of claim 1, wherein the gate electrode structure includes titaniumand nitrogen.
 9. The IC of claim 1, wherein the second portion of thebody is thinner than at least one of the source region and the drainregion.
 10. The IC of claim 1, wherein at least one of the first andthird portions of the body includes a higher concentration of oxygenvacancies in the oxide semiconductor material, relative to the secondportion.
 11. The IC of claim 1, further comprising a first contactstructure wrapped around the first portion of the body, and a secondcontact structure wrapped around the third portion of the body, thefirst and second contact structures comprising metal.
 12. The IC ofclaim 11, further comprising at least one of a first gate spacer betweenthe gate electrode structure and the first contact structure and asecond gate spacer between the gate electrode structure and the secondcontact structure.
 13. The IC of claim 1, wherein: a thickness of thebody in a vertical direction is in a range of 1 nanometer to 20nanometers; and a length of the body in a horizontal direction from thesource region to the drain region is in the range of 5 nanometers to 100nanometers, as measured from respective outermost portions of the sourceand drain regions.
 14. A computing system comprising the IC of claim 1.15. An integrated circuit (IC) comprising: a first body of oxidesemiconductor material, the first body including first, second, andthird portions, the second portion of the first body between the firstand third portions of the first body, the first portion of the firstbody being a first source region and the third portion of the first bodybeing a first drain region, and the second portion of the first bodyhaving a cross-section with a maximum lateral width greater than amaximum vertical height; a second body of oxide semiconductor material,the second body including first, second, and third portions, the secondportion of the second body between the first and third portions of thesecond body, the first portion of the second body being a second sourceregion and the third portion of the second body being a second drainregion, the second portion of the second body having a cross-sectionwith a maximum lateral width greater than a maximum vertical height, andthe second body being below the first body; and a gate structure thatwraps around the second portions of the first and second bodies.
 16. TheIC of claim 15, wherein the gate structure comprises: a gate dielectricthat includes a high-k dielectric material including hafnium; and a gateelectrode that includes titanium and nitrogen.
 17. The IC of claim 15,wherein the oxide semiconductor material includes oxygen and one or moreof indium, gallium, zinc, aluminum, tin, copper, arsenic, phosphorus,silicon, and germanium.
 18. The IC of claim 15, wherein the gatestructure comprises: a gate dielectric that includes a high-k dielectricmaterial; and a gate electrode.
 19. The IC of claim 15, wherein at leastone of the first and third portions of the first body or the second bodyincludes a higher concentration of oxygen vacancies in the oxidesemiconductor material, relative to the second portion.
 20. Anintegrated circuit (IC) comprising: a first body of oxide semiconductormaterial, the first body including first, second, and third portions,the second portion of the first body between the first and thirdportions of the first body, the first portion of the first body being afirst source region and the third portion of the first body being afirst drain region, and the second portion having a cross-section with amaximum lateral width greater than a maximum vertical height; a secondbody of oxide semiconductor material, the second body including first,second, and third portions, the second portion of the second bodybetween the first and third portions of the second body, the firstportion of the second body being a second source region and the thirdportion of the second body being a second drain region, the second bodybeing below the first body; a gate structure that wraps around thesecond portions of the first and second bodies; a first contactstructure that wraps around the first portions of the first and secondbodies; and a second contact structure that wraps around the thirdportions of the first and second bodies, the first and second contactstructures comprising metal.